Remove unused blink::WebStorageArea::memoryBytesUsedByCache().

content/renderer/dom_storage/local_storage_area.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/dom_storage/local_storage_area.h"
 
 #include "content/common/storage_partition_service.mojom.h"
 
 using blink::WebString;
 using blink::WebURL;
@@ skipping 29 matching lines @@
     WebStorageArea::Result& result) {
 }
 
 void LocalStorageArea::removeItem(
     const WebString& key, const WebURL& page_url) {
 }
 
 void LocalStorageArea::clear(const WebURL& page_url) {
 }
 
-size_t LocalStorageArea::memoryBytesUsedByCache() const {
-  return 0u;
-}
-
 void LocalStorageArea::KeyChanged(mojo::Array<uint8_t> key,
                                   mojo::Array<uint8_t> new_value,
                                   mojo::Array<uint8_t> old_value,
                                   const mojo::String& source) {
 }
 
 void LocalStorageArea::KeyDeleted(mojo::Array<uint8_t> key,
                                   const mojo::String& source) {
 }
 
 void LocalStorageArea::AllDeleted(const mojo::String& source) {
 }
 
 }  // namespace content